Power transmission control device for vehicle

ABSTRACT

A power transmission control device is used for a hybrid vehicle including an internal combustion engine and a motor (MG) as power sources, and includes a manual transmission and a friction clutch. A torque of the motor (MG torque) is generally adjusted to the smaller one (=MG torque final reference value) of an MG torque reference value determined based on an accelerator opening and an MG torque limit value determined based on a clutch return stroke. Based on satisfaction of a predetermined condition relating to a clutch pedal operation performed by a driver, the MG torque is intentionally adjusted to a value shifted from the MG torque final reference value in place of the MG torque final reference value. As a result, a driving force which is more appropriate or better meets a driver&#39;s intention can be obtained.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.13/994,920, filed Jun. 17, 2013, now allowed, which is a National StageApplication of PCT/JP2011/068508, filed Aug. 15, 2011, the entireties ofwhich are incorporated herein by reference, and claims the benefit under35 USC §119(a)-(d) of Japanese Patent Application No. 2010-291784, filedDec. 28, 2010.

FIELD OF THE INVENTION

The present invention relates to a power transmission control device fora vehicle, and more particularly, to a power transmission controldevice, which is to be used for a vehicle including a first power source(for example, an internal combustion engine) and a second power source(for example, an electric motor) as power sources, and includes afriction clutch.

BACKGROUND OF THE INVENTION

Conventionally, a so-called hybrid vehicle including an engine and anelectric motor (an electric motor and an electric power generator) aspower sources is widely known (for example, see Patent Literature 1). Inrecent years, a vehicle (hereinafter referred to as “HV-MT vehicle”),which is a hybrid vehicle and is provided with a manual transmission anda friction clutch, has been under development. In this context, “manualtransmission” is a transmission (so-called MT) without a torqueconverter, in which a gear position is selected based on a shiftposition of a shift lever operated by a driver. Moreover, the “frictionclutch” is a clutch interposed between an output shaft of an internalcombustion engine and an input shaft of the manual transmission, and anengaged state of the friction plate changes in accordance with anoperation amount of a clutch pedal operated by the driver. Now, a torqueof the output shaft of the internal combustion engine is hereinafterreferred to as “internal-combustion-engine torque,” and a torque of theoutput shaft of the electric motor is referred to as “electric-motortorque.”

CITATION LIST Patent Literature

-   [PTL 1] JP 2000-224710 A

SUMMARY OF THE INVENTION

On the HV-MT vehicle, a configuration of connecting the output shaft ofthe electric motor to any one of the output shaft of the internalcombustion engine, the input shaft of the transmission, and the outputshaft of the transmission may be employed. Now, a configuration in whichthe output shaft of the electric motor is connected to the input shaftof the transmission or the output shaft of the transmission isconsidered.

In this case, the electric-motor torque can be adjusted in the followingmanner based on, for example, an operation amount of an acceleratorpedal (accelerator opening) and an operation amount of a clutch pedal.Specifically, first, a first relationship (see FIG. 2 referred to later)between the accelerator opening and a “reference value of theelectric-motor torque (electric-motor torque reference value)” and asecond relationship (see FIG. 3 referred to later) between the operationamount of the clutch pedal and an “upper-limit value of theelectric-motor torque (electric-motor torque limit value)” aredetermined and stored in advance through an experiment or the like. Acurrent electric-motor torque reference value is determined based on acurrent accelerator opening and the above-mentioned first relationship.A current electric-motor torque limit value is determined based on acurrent operation amount of the clutch pedal and the above-mentionedsecond relationship. A current electric-motor torque is adjusted to thesmaller one of the determined current electric-motor torque referencevalue and the determined current electric-motor torque limit value. Thesmaller value is hereinafter referred to as “electric-motor torque finalreference value.”

In a case where an operation of the clutch pedal is related, byadjusting the electric-motor torque to the electric-motor torque finalreference value in this manner, driving feeling using the electric-motortorque of the HV-MT vehicle can be made close to driving feeling usingthe internal-combustion-engine torque of an ordinary MT vehicle. Theordinary MT vehicle refers to a conventionally widely known vehicleincluding a manual transmission and a friction clutch, and mounted withonly an internal combustion engine as a power source.

A case where a driver who is inexpert (inexperienced) in the operationof the clutch pedal drives the HV-MT vehicle and operates the clutchpedal for a shift operation or the like is supposed. In this case,because of an inappropriate operation of the clutch pedal, a pattern ofchange of the electric-motor torque limit value (hence, theelectric-motor torque final reference value) determined based on theoperation amount of the clutch pedal may be determined to be a patterndifferent from an appropriate pattern. As a result, if theelectric-motor torque is continuously adjusted to the electric-motortorque final reference value, there may arise a problem in that itbecomes difficult to obtain an appropriate driving force (for example, agear shift shock becomes larger) or the like.

On the other hand, under some situations, there is also a case where adriving force better meeting a driver's intention is obtained byintentionally adjusting the electric-motor torque to a value differentfrom the electric-motor torque final reference value rather than bycontinuously adjusting the electric-motor torque to the electric-motortorque final reference value. As described above, there are some caseswhere it is preferred to generate an appropriate driving force byintentionally adjusting the electric-motor torque to the value differentfrom the electric-motor torque final reference value.

The present invention has been made to cope with the problem describedabove, and therefore has an object to provide a power transmissioncontrol device for an HV-MT vehicle, in particular, capable ofgenerating an appropriate driving force to be transmitted to a drivewheel by intentionally adjusting an electric-motor torque to a valuedifferent from an electric-motor torque final reference value in a casewhere an operation of a clutch operation member is related.

A power transmission control device for a vehicle according to thepresent invention is used for a hybrid vehicle including a first powersource and a second power source as power sources. The powertransmission control device includes a transmission, a friction clutch,and control means. The first power source and the second power sourcemay respectively be an internal combustion engine and an electric motor,an electric motor and an internal combustion engine, or both electricmotors. In the following, the description is continued assuming that thefirst power source and the second power source are respectively theinternal combustion engine and the electric motor.

The transmission may be an automatic transmission including a torqueconvertor, but the transmission is preferred to be a manual transmissionwithout a torque converter, in which a gear position is selected basedon a shift position of a shift operation member operated by a driver.The transmission includes an input shaft for inputting a power from anoutput shaft of the internal combustion engine, and an output shaft foroutputting the power to a drive wheel of the vehicle. The electric motorhas an output shaft connected to the input shaft or the output shaft ofthe transmission.

The friction clutch is interposed between the output shaft of theinternal combustion engine and the input shaft of the transmission forselectively realizing any one of the fully disengaged state, thepartially engaged state, and the fully engaged state, in accordance withan operation amount of the clutch operation member operated by thedriver. When the clutch operation member is not operated by the driver,the friction clutch realizes the fully engaged state. An operationamount of the clutch operation member is detected by second detectionmeans.

The control means controls a torque of the output shaft of the internalcombustion engine (internal-combustion-engine torque) and a torque ofthe output shaft of the electric motor (electric-motor torque). Inparticular, the electric-motor torque is adjusted as follows. Anelectric-motor torque reference value is first determined based on astored first relationship between an operation amount of theacceleration operation member and a reference of the electric-motortorque (electric-motor torque reference value), and the detectedoperation amount of the acceleration operation member. An electric-motortorque limit value is determined based on a stored second relationshipbetween the operation amount of the clutch operation member and an upperlimit of the electric-motor torque (electric-motor torque limit value),and the detected operation amount of the clutch operation member. Theoperation amount of the acceleration operation member is detected byfirst detection means.

Generally (when a predetermined condition relating to the operation ofthe clutch operation member performed by the driver is not satisfied),the electric-motor torque is adjusted to the smaller one (electric-motortorque final reference value) of the determined electric-motor torquereference value and electric-motor torque limit value. On the otherhand, based on the satisfaction of the predetermined condition relatingto the operation of the clutch operation member performed by the driver,the electric-motor torque is exceptionally adjusted to a “value shiftedfrom the electric-motor torque final reference value” in place of theelectric-motor torque final reference value.

With the configuration described above, in association with theoperation of the clutch operation member performed by the driver, theelectric-motor torque is intentionally adjusted to the value differentfrom the electric-motor torque final reference value so that anappropriate driving force can be generated. As a result, a driving forcewhich is more appropriate or better meets a driver's intention can beobtained. A specific method of generating an appropriate driving forceby using the electric-motor torque under various situations is describedlater.

In general, a configuration may be configured as follows. In the secondrelationship, the second torque limit value is maintained to zero whenthe operation amount of the clutch operation member falls within a rangeon the fully disengaged state side with respect to a “meet start point”(the operation amount of the clutch operation member, corresponding to atiming at which the friction clutch transitions from the fullydisengaged state to the partially engaged state), the second torquelimit value is maintained to a maximum value when the operation amountof the clutch operation member falls within a range on the fully engagedstate side with respect to a “release start point” (the operation amountof the clutch operation member, corresponding to a timing at which thefriction clutch transitions from the fully engaged state to thepartially engaged state), and the second torque limit value increasesfrom zero as the operation amount of the clutch operation member movesfrom the “meet start point” to the “release start point” when theoperation amount of the clutch operation member is between the “meetstart point” and the “release start point.”

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A schematic configuration diagram of an HV-MT vehicle in which apower transmission control device according to an embodiment of thepresent invention is mounted.

FIG. 2 A graph showing a map defining the relationship between anaccelerator opening and an MG-torque reference value, which is referredto by the power transmission control device illustrated in FIG. 1.

FIG. 3 A graph showing a map defining the relationship between a clutchreturn stroke and an MG torque limit value, which is referred to by thepower transmission control device illustrated in FIG. 1.

FIG. 4 A time chart illustrating an example of an operation in a casewhere an MG torque is continuously adjusted to an MG torque finalreference value during a shift operation.

FIG. 5 A time chart illustrating an example of an operation in a firstcase where the MG torque is intentionally adjusted to a value differentfrom the MG torque final reference value during the shift operation.

FIG. 6 A time chart illustrating an example of an operation in a secondcase where the MG torque is intentionally adjusted to the valuedifferent from the MG torque final reference value during the shiftoperation.

FIG. 7 A time chart illustrating an example of an operation in a thirdcase where the MG torque is intentionally adjusted to the valuedifferent from the MG torque final reference value during the shiftoperation.

FIG. 8 A time chart illustrating an example of an operation in a fourthcase where the MG torque is intentionally adjusted to the valuedifferent from the MG torque final reference value during the shiftoperation.

FIG. 9 A time chart illustrating an example of an operation in a fifthcase where the MG torque is intentionally adjusted to the valuedifferent from the MG torque final reference value during the shiftoperation.

FIG. 10 A time chart illustrating an example of an operation in a sixthcase where the MG torque is intentionally adjusted to the valuedifferent from the MG torque final reference value during the shiftoperation.

FIG. 11 A time chart illustrating an example of an operation in aseventh case where the MG torque is intentionally adjusted to the valuedifferent from the MG torque final reference value during the shiftoperation.

FIG. 12 A time chart illustrating an example of an operation in aneighth case where the MG torque is intentionally adjusted to the valuedifferent from the MG torque final reference value during the shiftoperation.

DETAILED DESCRIPTION OF THE INVENTION

A description is now given of a power transmission control device for avehicle according to an embodiment of the present invention, referringto the drawings.

(Configuration)

FIG. 1 illustrates a schematic configuration of a vehicle in which apower transmission control device (hereinafter referred to as “thisdevice”) according to the embodiment of the present invention ismounted. This vehicle is a hybrid vehicle including an engine E/G and amotor/generator M/G as power sources, and also including a manualtransmission M/T without a torque converter, and a friction clutch C/T.In other words, this vehicle is the above-mentioned HV-MT vehicle.

The engine E/G is a known internal combustion engine, and is, forexample, a gasoline engine using gasoline as a fuel or a diesel engineusing light oil as a fuel.

The manual transmission M/T is a transmission without a torqueconverter, in which a gear position is selected based on a shiftposition of a shift lever SL operated by a driver. The M/T includes aninput shaft for inputting a power from the output shaft of the E/G, andan output shaft for outputting a power to a drive wheel of the vehicle.The M/T includes, for example, four forward gear positions (first tofourth), and one reverse gear position (R).

The gear positions of the M/T may be mechanically selected/changed byusing a link mechanism or the like, which mechanically couples the shiftlever SL and a sleeve (not shown) inside the M/T, based on the shiftposition of the shift lever SL, or may be selected/changed electrically(by means of the so-called by-wire method) by using a driving force ofan actuator which operates based on a detection result by a sensor(sensor S2 described later) for detecting the shift position of theshift lever SL.

The friction clutch C/T is interposed between the output shaft of theE/G and the input shaft of the M/T. The C/T is a known clutch having anengaged state of a friction plate (more specifically, with respect to aflywheel, which integrally rotates with the output shaft of the E/G, aposition in the axial direction of the friction plate, which integrallyrotates with the input shaft of the M/T), which changes in accordancewith an operation amount (depressed amount) of a clutch pedal CPoperated by the driver.

The engaged state includes a fully engaged state, a partially engagedstate, and a fully disengaged state. The fully engaged state refers to astate of transmitting the power without a slip. The partially engagedstate refers to a state of transmitting the power with a slip. The fullydisengaged state refers to a state of not transmitting the power. Now,from a fully depressed state of the clutch pedal CP, an operation amountin a returning direction of the clutch pedal CP is hereinafter referredto as “clutch return stroke.”

The clutch return stroke is “0” in a state in which the clutch pedal CPis fully depressed, and takes the maximum value in a state in which theclutch pedal CP is released (is not operated). As the clutch returnstroke increases from “0”, the C/T transitions from the fully disengagedstate, via the partially engaged state, to the fully engaged state.

The engaged state of the C/T (the axial position of the friction plate)may be mechanically adjusted in accordance with on the operation amountof the CP by using a link mechanism or the like for mechanicallycoupling the clutch pedal CP and the C/T (friction plate), or may beadjusted electrically (by means of the so-called by-wire method) byusing a driving force of an actuator which operates based on a detectionresult by a sensor (sensor S1 described later) for detecting theoperation amount of the CP.

The motor/generator M/G has one of known structures (such as ACsynchronous motor), and, for example, a rotor (not shown) is configuredso as to integrally rotate with the output shaft of the M/G. The outputshaft of the M/G is connected so as to be able to transmit a powerthrough an intermediation of a known gear train or the like to theoutput shaft of the M/T.

As indicated by a broken line in FIG. 1, a powerconnection/disconnection mechanism CHG for selectively realizing the“engaged state” in which the power is transmitted and the “disengagedstate” in which the power is not transmitted may be interposed betweenthe C/T and the M/T. A torque of the output shaft of the E/G ishereinafter referred to as “EG torque,” whereas a torque of the outputshaft of the M/G is hereinafter referred to as “MG torque.” The CHG isplaced in the “disengaged state” when the vehicle runs only with the MGtorque (>0) in a state in which the clutch pedal CP is not operated(namely, the C/T is in the fully engaged state) and the like. In thiscase, by placing the CHG in the “disengaged state,” the rotation of theinput shaft of the M/T can be prevented from being transmitted to theoutput shaft of the E/G through the C/T.

This device includes the clutch operation amount sensor S1 for detectingthe clutch return stroke of the clutch pedal CP, the shift positionsensor S2 for detecting the position of the shift lever SL, anaccelerator operation amount sensor S3 for detecting an operation amountof an accelerator pedal AP (accelerator opening), a brake operationamount sensor S4 for detecting an operation amount of a brake pedal BP(such as depressing force and presence/absence of operation), a wheelspeed sensor S5 for detecting a speed of a wheel, a rotation speedsensor S6 for detecting a rotation speed Ne of the output shaft of theE/G, and a rotation speed sensor S7 for detecting a rotation speed Ni ofthe input shaft of the M/T.

Further, this device includes an electronic control unit ECU. The ECUcontrols, based on information from the above-mentioned sensors S1 to S7and other sensors and the like, and other such information, a fuelinjection amount (opening of a throttle valve) of the E/G, therebycontrolling the EG torque, and controls an inverter (not shown), therebycontrolling the MG torque. Further, in a case where the powerconnection/disconnection mechanism CHG is provided, the ECU controls thestate of CHG.

Specifically, a ratio between the EG torque and the MG torque isadjusted based on the information from the above-mentioned sensors S1 toS7 and other sensors and the like, and other such information. Themagnitudes of the EG torque and the MG torque are respectively adjustedmainly based on the accelerator opening. In particular, in this example,the MG torque is adjusted in the following manner.

Specifically, first, based on a map shown in FIG. 2 and a currentaccelerator opening, an “MG torque reference value” is determined. TheMG torque reference value is determined to be a larger value as theaccelerator opening increases. The characteristic of the MG torquereference value with respect to the accelerator opening can change inaccordance with various states (such as a ratio between the EG torqueand the MG torque) other than the accelerator opening.

Moreover, based on a map shown in FIG. 3 and a current clutch returnstroke, an “MG torque limit value” is determined. The MG torque limitvalue is defined by using a meet start point and a release start point.The meet start point is a clutch return stroke corresponding to a timingat which the C/T transitions from the fully disengaged state to thepartially engaged state, and the release start point is a clutch returnstroke corresponding to a timing at which the C/T transitions from thefully engaged state to the partially engaged state.

In this example, in a range of the clutch return stroke from “0” to the“meet start point” (namely, a range corresponding to the fullydisengaged state of the C/T; refer to “range a” of FIG. 3), the MGtorque limit value maintains “0”, in a range of the clutch return strokelarger than the “release start point” (namely, a range corresponding tothe fully engaged state of the C/T; refer to “range c” of FIG. 3), theMG torque limit value maintains the “maximum value,” and, in a range ofthe clutch return stroke between the “meet start point” and the “releasestart point” (namely, a range corresponding to the partially engagedstate of the C/T; refer to “range b” of FIG. 3), as the clutch returnstroke transitions from the “meet start point” to the “release startpoint,” the MG torque limit value increases from “0.” Theabove-mentioned “maximum value” of the MG torque limit value can be set,for example, to a value equivalent to the current “MG torque referencevalue” described above. The maps shown in FIGS. 2 and 3 are stored in anupdatable manner in a predetermined area of a memory of the ECU.

Then, the MG torque is generally adjusted to a smaller value(hereinafter referred to as “MG torque final reference value”) out ofthe determined “MG torque reference value” and “MG torque limit value”described above. That is, the MG torque is usually adjusted, within arange of the “MG torque limit value” determined based on the clutchreturn stroke, to a value based on the “MG torque reference value” (=MGtorque final reference value) determined based on the acceleratoropening. In this way, by adjusting the MG torque so as to coincide withthe MG torque final reference value, driving feeling using the MG torqueof the HV-MT vehicle can be made close to driving feeling using the EGtorque of the above-mentioned “ordinary MT vehicle”.

(Generation of Appropriate Driving Torque by MG Torque)

It is only when the operation of the clutch pedal is appropriate that anappropriate driving force (for example, driving force with a small gearshift shock) is obtained by adjusting the MG torque so that the MGtorque coincides with the MG torque final reference value as describedabove. In other words, for example, when a driver who is inexpert(inexperienced) in the operation of the clutch pedal performs aninappropriate operation of the clutch pedal for a shift operation or thelike, a pattern of change of the MG torque limit value (hence, the MGtorque final reference value) determined based on the clutch returnstroke may be determined to be a pattern different from an appropriatepattern. As a result, if the MG torque is continuously adjusted to theMG torque final reference value, there may arise a problem in that itbecomes difficult to obtain an appropriate driving force (for example,the gear shift shock becomes larger) or the like.

In addition, under some situations, there is also a case where a drivingforce which better meets a driver's intention is obtained byintentionally adjusting the MG torque to a value different from the MGtorque final reference value rather than by continuously adjusting theMG torque to the MG torque final reference value. As described above,there are some cases where it is preferred to generate an appropriatedriving force by intentionally adjusting the MG torque to the valuedifferent from the MG torque final reference value.

The above-mentioned case is now described referring to FIGS. 4 to 12.FIG. 4 illustrates an example of an operation in a case where the MGtorque is continuously adjusted to the MG torque final reference valueduring the shift operation (specifically, an appropriate driving forceis not generated by using the MG torque). FIGS. 5 to 12 each illustratean example where the MG torque is intentionally adjusted to a valuedifferent from the MG torque final reference value so as to generate anappropriate driving force under the same situations as those of theexample illustrated in FIG. 4. First, a description is given referringto FIG. 4.

The example illustrated in FIG. 4 assumes a case where the vehicle runsat a second speed by using only the MG torque (MG torque>0, EG torque=0)or by using both the EG torque and the MG torque (EG torque>0, MGtorque>0) before a time t1. After the time t1, the accelerator pedal AP,the clutch pedal CP, and the shift lever SL are operated in cooperationwith each other for a shift-up operation (shift operation) from thesecond speed to a third speed.

In this example, focusing on the operation of the clutch pedal CP, theclutch pedal CP is operated from the time t1 to a time t6. Specifically,at the time t1, the operation of the clutch pedal CP is started. At atime t2, the clutch return stroke transitions from the range c to therange b (the C/T transitions from the fully engaged state to thepartially engaged state). At a time t3, the clutch return stroketransitions from the range b to the range a (the C/T transitions fromthe partially engaged state to the fully disengaged state). At a timet4, the clutch return stroke transitions from the range a to the range b(the C/T transitions from the fully disengaged state to the partiallyengaged state). At a time t5, the clutch return stroke transitions fromthe range b to the range c (the C/T transitions from the partiallyengaged state to the fully engaged state). At the time t6, the operationof the clutch pedal CP is terminated.

In this example, focusing on a change in the MG torque (=MG torque finalreference value), before the time t2, the MG torque is adjusted to avalue which is equal to the MG torque reference value based on theaccelerator opening (see FIG. 2) because of the presence of the clutchreturn stroke in the range c. From the time t2 to the time t5, the MGtorque is adjusted to a value which is equal to the MG torque limitvalue based on the clutch return stroke (see FIG. 3) because of thepresence of the clutch return stroke in the range b or a. After the time5, the MG torque is adjusted to the value which is equal to the MGtorque reference value based on the accelerator opening (see FIG. 2)because of the presence of the clutch return stroke in the range c.

Now, referring to FIGS. 5 to 12, first to eighth cases in which the MGtorque is intentionally adjusted to a value different from the MG torquefinal reference value so as to generate an appropriate driving forceunder the above-mentioned situations illustrated in FIG. 4 are describedin order. In FIGS. 5 to 12, a broken line indicates a change in the casewhere the MG torque is continuously adjusted to the MG torque finalreference value by way of comparison.

<First Case>

An example illustrated in FIG. 5 mainly assumes a case where the vehicleruns by using only the MG torque (MG torque>0, EG torque=0). In thisexample, for each of the timing (time t2) at which the friction clutchC/T transitions from the fully engaged state to the partially engagedstate, the timing (time t3) at which the C/T transitions from thepartially engaged state to the fully disengaged state, the timing (timet4) at which the C/T transitions from the fully disengaged state to thepartially engaged state, and the timing (time t5) at which the C/Ttransitions from the partially engaged state to the fully engaged state,the MG torque is adjusted to a value shifted from the MG torque finalreference value for an extremely short period including thecorresponding timing. Each of the timings can be acquired, predicted, orestimated based on the result of detection of the clutch return stroke.

In this example, for each of the time t2 and the time t3 relating to adeceleration operation of the vehicle, the MG torque is adjusted to avalue smaller than the MG torque final reference value for an extremelyshort period including the corresponding time. For each of the time t4and the time t5 relating to an acceleration operation of the vehicle,the MG torque is adjusted to a value larger than the MG torque finalreference value for an extremely short period including thecorresponding time.

By intentionally adjusting the MG torque to a value different from theMG torque final reference value as in this example, an extremely smallshock can be made to be perceived by the driver in synchronization withthe timing at which the engaged state of the friction clutch C/Tchanges. As a result, in particular, the driver who is inexpert(inexperienced) in the operation of the clutch pedal can learn by anexperience the clutch return stroke (position of the friction clutchC/T) corresponding to the timing at which the engaged state of thefriction clutch C/T changes. Therefore, the operation of the clutchpedal by the driver described above can more rapidly improve.

Although the MG torque is adjusted to a value shifted from the MG torquefinal reference value in synchronization with each of the timingscorresponding to the times t2 to t5 in the example illustrated in FIG.5, the MG torque may be adjusted to a value shifted from the MG torquefinal reference value in synchronization with only a part of the timingscorresponding to the times t2 to t5. Moreover, although the MG torque isadjusted to the value smaller than the MG torque final reference valuein synchronization with each of the timings corresponding to the timest2 and t3 in the example illustrated in FIG. 5, the MG torque may beadjusted to a value larger than the MG torque final reference value insynchronization with each of the timings corresponding to the times t2and t3. Similarly, although the MG torque is adjusted to the valuelarger than the MG torque final reference value in synchronization witheach of the timings corresponding to the times t4 and t5, the MG torquemay be adjusted to a value smaller than the MG torque final referencevalue in synchronization with each of the timings corresponding to thetimes t4 and t5.

<Second Case>

An example illustrated in FIG. 6 assumes a case where the vehicle runsby using both the EG torque and the MG torque (EG torque>0, MGtorque>0). In this example, based on the determination that a “speed ofchange (gradient of change) in the clutch return stroke at the time oftransition of the friction clutch C/T from the partially engaged stateto the fully engaged state (immediately before the time t5) is equal toor larger than a predetermined value,” the MG torque is adjusted to avalue obtained by superimposing a “counter vibration pattern” on the MGtorque final reference value after the friction clutch C/T transitionsfrom the partially engaged state to the fully engaged state (after thetime t5).

Here, the “counter vibration pattern” is a vibration pattern cancellingout a vibration of the driving torque (torque to be transmitted to thedrive wheel of the vehicle), which is supposed to be generated after thefriction clutch C/T transitions to the fully engaged state. When thespeed of change in the clutch return stroke at the time of transition ofthe friction clutch C/T from the partially engaged state to the fullyengaged state is large, vibrations are likely to be generated in adriving system (hence, in the driving torque to be transmitted to thedrive wheel) immediately after the transition (see a broken line of FIG.6). The generation of vibrations is mainly due to a “difference inrotation speed between the output shaft of the E/G and the input shaftof the M/T” immediately before the transition of the friction clutch C/Tto the fully engaged state.

The vibration pattern (changes in amplitude and period with respect totime) of the driving system greatly depends on the speed of change inthe clutch return stroke described above. Therefore, the “countervibration pattern” (changes in amplitude and period with respect totime) for cancelling out the vibration pattern can also be computedbased on the speed of change in the clutch return stroke describedabove. Specifically, for example, the “counter vibration pattern” can becomputed based on a map defining the relationship between the clutchreturn stroke and the “counter vibration pattern,” which is created inadvance, and the actually acquired clutch return stroke.

By intentionally adjusting the MG torque to the value shifted from theMG torque final reference value as in this example, the vibration in thedriving system (hence, the torque to be transmitted to the drive wheel),which may be generated immediately after the transition of the frictionclutch C/T from the partially engaged state to the fully engaged state,can be suppressed in the case where the speed of change in the clutchreturn stroke at the time of transition of the C/T is high (see a solidline of FIG. 6).

<Third Case>

An example illustrated in FIG. 7 assumes a case where the vehicle runsby using both the EG torque and the MG torque (EG torque>0, MGtorque>0). In this example, based on the determination that a “speed ofchange (gradient of change) in the clutch return stroke at the time oftransition of the friction clutch C/T from the fully disengaged state tothe partially engaged state (immediately before the time t4) is equal toor larger than a predetermined value,” the MG torque is adjusted so thata gradient of increase of the MG torque becomes smaller than that of theMG torque final reference value after the friction clutch C/Ttransitions from the fully disengaged state to the partially engagedstate (after the time t4).

When the speed of change in the clutch return stroke at the time oftransition of the friction clutch C/T from the fully disengaged state tothe partially engaged state is high, the vibration is likely to begenerated in the driving system (hence, the driving torque to betransmitted to the drive wheel) after the subsequent transition to thefully engaged state, for the same reason as that described above in thesecond case (see a broken line of FIG. 7).

When the speed of change in the clutch return stroke at the time oftransition of the friction clutch C/T from the fully disengaged state tothe partially engaged state is high, a gradient of subsequent increaseof the MG torque can be reduced by intentionally adjusting the MG torqueto the value shifted from the MG torque final reference value as in thisexample. The reduction in gradient of increase can contribute to thesuppression of vibrations in the driving system (hence, the torque to betransmitted to the drive wheel), which may be generated after thesubsequent transition to the fully engaged state (see a solid line ofFIG. 7).

<Fourth Case>

An example illustrated in FIG. 8 assumes a case where the vehicle runsby using only the MG torque (MG torque>0, EG torque=0). In this example,based on the determination that a “speed of change (gradient of change)in the clutch return stroke at the time of transition of the frictionclutch C/T from the fully disengaged state to the partially engagedstate (immediately before the time t4) is equal to or larger than apredetermined value,” the MG torque is adjusted so that a gradient ofincrease of the MG torque becomes larger than that of the MG torquefinal reference value after the friction clutch C/T transitions from thefully disengaged state to the partially engaged state (after the timet4).

When the speed of change in the clutch return stroke at the time oftransition of the friction clutch C/T from the fully disengaged state tothe partially engaged state is high, it is considered that the driverdesires an “immediate significant acceleration of the vehicle” in manycases.

When the speed of change in the clutch return stroke at the time oftransition of the friction clutch C/T from the fully disengaged state tothe partially engaged state is high, a gradient of subsequent increaseof the MG torque can be increased by intentionally adjusting the MGtorque to the value shifted from the MG torque final reference value asin this example. Therefore, the vehicle can be immediately significantlyaccelerated. As a result, the driving force which better meets thedriver's intention can be obtained. When the vehicle runs by using onlythe MG torque as in this example, the power connection/disconnectionmechanism CHG is generally maintained in the disengaged state.Therefore, even when the speed of change (gradient of change) in theclutch return stroke is large, the above-mentioned vibration in thedriving system (hence, the driving torque to be transmitted to the drivewheel) is not generated.

<Fifth Case>

An example illustrated in FIG. 9 assumes a case where the vehicle runsby using only the MG torque (MG torque>0, EG torque=0) or by using boththe EG torque and the MG torque (EG torque>0, MG torque>0). Moreover,this example assumes a vehicle having a normal mode (first mode) and asport mode (second mode) in which the vehicle is accelerated to a higherspeed than in the normal mode as driving modes, and means for switchingthe driving modes (selector switch or the like).

In this example, based on the determination of “selection of the sportmode as the driving mode,” the MG torque is adjusted so that a gradientof increase of the MG torque becomes larger than that of the MG torquefinal reference value after the transition of the friction clutch C/Tfrom the fully disengaged state to the partially engaged state (afterthe time t4).

When the sport mode is selected as the driving mode, it is consideredthat the driver desires an “immediate significant acceleration of thevehicle” in many cases. When the sport mode is selected, the gradient ofincrease of the MG torque after the transition of the friction clutchC/T from the fully disengaged state to the partially engaged state canbe increased by intentionally adjusting the MG torque to a value shiftedfrom the MG torque final reference value as in this example. Therefore,the vehicle can be immediately significantly accelerated. As a result,the driving force which better meets the driver's intention can beobtained.

<Sixth Case>

An example illustrated in FIG. 10 assumes a case where the vehicle runsby using only the MG torque (MG torque>0, EG torque=0) or by using boththe EG torque and the MG torque (EG torque>0, MG torque>0). In thisexample, in the case where a gradient of decrease (>0) of the MG torquefinal reference value exceeds a predetermined value (>0) at the time oftransition of the friction clutch C/T from the fully engaged state tothe partially engaged state and the fully disengaged state, the MGtorque is adjusted so that the gradient of decrease of the MG torquebecomes equal to (is limited to) the predetermined value.

When the gradient of decrease (>0) of the MG torque final referencevalue is large, the gradient of decrease of the MG torque is limited byintentionally adjusting the MG torque to the value shifted from the MGtorque final reference value as in this example. As a result, a shockwhich may be generated in the process of transition of the frictionclutch C/T from the fully engaged state to the partially engaged stateand the fully disengaged state can be alleviated.

<Seventh Case>

An example illustrated in FIG. 11 assumes a case where the vehicle runsby using only the MG torque (MG torque>0, EG torque=0) or by using boththe EG torque and the MG torque (EG torque>0, MG torque>0). In thisexample, when the friction clutch C/T transitions from the fully engagedstate to the partially engaged state and the fully disengaged state, theMG torque is adjusted to a “value obtained by performing delayprocessing on the MG torque final reference value.” Here, the term“delay processing” refers to, for example, processing for providing adead time, primary delay processing, and the like.

When the speed of change in the MG torque final reference value is high,a change in the speed of change is large, or the like, the MG torquerelatively gently decreases by intentionally adjusting the MG torque toa value shifted from the MG torque final reference value as in thisexample. As a result, in a process of the transition of the frictionclutch C/T from the fully engaged state to the partially engaged stateand the fully disengaged state, feeling of gentle change can be given tothe driver.

<Eighth Case>

An example illustrated in FIG. 12 assumes a case where the vehicle runsby using only the EG torque (MG torque=0, EG torque>0). In this example,in a process of the transition of the friction clutch C/T from the fullyengaged state through the partially engaged state, the fully disengagedstate, and the partially engaged state to return to the fully engagedstate, it is first determined whether the vehicle is in an acceleratingdirection or a decelerating direction based on the determination of“transition of the C/T from the fully disengaged state to the partiallyengaged state”. The determination is performed based on, for example,the accelerator opening.

Then, after the transition of the C/T from the fully disengaged state tothe partially engaged state, the MG torque is adjusted to a value for anorientation corresponding to the determined direction. Specifically, theMG torque is adjusted to a value for an orientation for accelerating thevehicle when the vehicle is determined to be in the accelerationdirection and to a value for an orientation for decelerating the vehiclewhen the vehicle is determined to be in the deceleration direction.

By intentionally adjusting the MG torque to a value shifted from the MGtorque final reference value as in this example, a “play” due tobacklash etc. in a meshing portion between gears in the driving systemcan be eliminated in an early stage immediately after the transition ofthe C/T from the fully disengaged state to the partially engaged state.

The present invention is not limited to the embodiment described above,and various variations can be adopted within the scope of the presentinvention. For example, in the embodiment described above, the E/G isused as the first power source, whereas the M/G is used as the secondpower source. However, the M/G may be used for each of both the firstpower source and the second power source.

Moreover, although the output shaft of the M/G is connected to theoutput shaft of the M/T (through an intermediation of a known gear trainor the like) so that the power can be transmitted in the embodimentdescribed above, the output shaft of the M/G may be connected to theinput shaft of the M/T (through an intermediation of a known gear trainor the like) so that the power can be transmitted.

In addition, although the manual transmission M/T without a torqueconverter is used as the “transmission” in the embodiment describedabove, an automatic transmission including a torque converter may beused instead.

REFERENCE SIGNS LIST

M/T . . . transmission, E/G . . . engine, C/T . . . clutch, M/G . . .motor/generator, CP . . . clutch pedal, AP . . . accelerator pedal, S1 .. . clutch operation amount sensor, S2 . . . shift position sensor, S3 .. . accelerator operation amount sensor, S4 . . . brake operation amountsensor, S5 . . . wheel speed sensor, S6 . . . rotation speed sensor, S7. . . rotation speed sensor, ECU . . . electronic control unit

1. A power transmission control device for a vehicle, which is to beused for a vehicle comprising a first power source and a second powersource, the power transmission control device comprising: a transmissionincluding an input shaft for inputting a power from an output shaft ofthe first power source and an output shaft for outputting the power to adrive wheel of the vehicle, the second power source having an outputshaft connected to the input shaft or the output shaft; a frictionclutch interposed between the output shaft of the first power source andthe input shaft of the transmission, for realizing a fully engaged statein which the power is transmitted without a slip when a clutch operationmember to be operated by a driver is not operated and for realizing apartially engaged state in which the power is transmitted with the slipin accordance with an operation amount of the clutch operation member ora fully disengaged state in which the power is not transmitted; firstdetection means for detecting an operation amount of an accelerationoperation member for accelerating the vehicle, the accelerationoperation member being to be operated by the driver; second detectionmeans for detecting the operation amount of the clutch operation member;and control means for controlling a first torque corresponding to adriving torque for the output shaft of the first power source and asecond torque corresponding to a driving torque for the output shaft ofthe second power source, wherein the control means comprises: firstdetermination means for determining a second torque reference valuewhich is a reference of the second torque based on a stored firstrelationship between the operation amount of the acceleration operationmember and the second torque reference value, and the detected operationamount of the acceleration operation member; and second determinationmeans for determining a second torque limit value which defines an upperlimit of the second torque based on a stored second relationship betweenthe operation amount of the clutch operation member and the secondtorque limit value, and the detected operation amount of the clutchoperation member, and wherein the control means is configured to adjustthe second torque to a second torque final reference value correspondingto a smaller one of the determined second torque reference value and thedetermined second torque limit value, wherein the control means isconfigured to, in a case where the first torque is maintained to zero bystop of the first power source, and the vehicle runs by drive of thesecond power source by using only the second torque which is generatedby the second power source, when the friction clutch transitions fromthe fully engaged state through the partially engaged state, the fullydisengaged state, and the partially engaged state to return to the fullyengaged state by the operation of the clutch operation member for ashift operation of the transmission, detect a timing at which thefriction clutch transitions from the partially engaged state to thefully disengaged state based on the detected operation amount of theclutch operation member so as to adjust the second torque to a valueshifted from the second torque final reference value in synchronizationwith the detected timing.
 2. A power transmission control device for avehicle according to claim 1, wherein the control means is configuredto, in a case where the first torque is maintained to zero by stop ofthe first power source, and the vehicle runs by drive of the secondpower source by using only the second torque which is generated by thesecond power source, when the friction clutch transitions from the fullyengaged state through the partially engaged state, the fully disengagedstate, and the partially engaged state to return to the fully engagedstate by the operation of the clutch operation member for a shiftoperation of the transmission, detect respective timings of a timing atwhich the friction clutch transitions from the fully engaged state tothe partially engaged state, a timing at which the friction clutchtransitions from the partially engaged state to the fully disengagedstate, a timing at which the friction clutch transitions from the fullydisengaged state to the partially engaged state, and a timing at whichthe friction clutch transitions from the partially engaged state to thefully engaged state based on the detected operation amount of the clutchoperation member so as to adjust the second torque to a value shiftedfrom the second torque final reference value in synchronization with thedetected respective timings.
 3. A power transmission control device fora vehicle according to claim 1, wherein the power transmission controldevice is configured to, in the second relationship, maintain the secondtorque limit value to zero when the operation amount of the clutchoperation member falls within a range on the fully disengaged state sidewith respect to a meet start point corresponding to a timing at whichthe friction clutch transitions from the fully disengaged state to thepartially engaged state, to maintain the second torque limit value to amaximum value when the operation amount of the clutch operation memberfalls within a range on the fully engaged state side with respect to arelease start point corresponding to a timing at which the frictionclutch transitions from the fully engaged state to the partially engagedstate, and to increase the second torque limit value from zero as theoperation amount of the clutch operation member moves from the meetstart point to the release start point when the operation amount of theclutch operation member is between the meet start point and the releasestart point.